Habitat cues synergize to elicit chemically-mediated landing behavior in a specialist phytophagous insect, the grape berry moth

Authors: WOLFIN, MICHAEL - Cornell University; CHILSON III, RONALD - Cornell University; THRALL, JONATHAN - Hobart And William Smith Colleges; LIU, YUXI - Hobart And William Smith Colleges; VOLO, SARA - Hobart And William Smith Colleges; Cha, Dong; LOEB, GREGORY - Cornell University; LINN JR, CHARLES - Cornell University

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2020
Publication Date: 11/28/2020
Citation: Wolfin, M.S., Chilson III, R.R., Thrall, J., Liu, Y., Volo, S., Cha, D.H., Loeb, G.M., Linn Jr, C.E. 2020. Habitat cues synergize to elicit chemically-mediated landing behavior in a specialist phytophagous insect, the grape berry moth. Entomologia Experimentalis et Applicata. 168(12):880-889. https://doi.org/10.1111/eea.13003.
DOI: https://doi.org/10.1111/eea.13003

Interpretive Summary: Insect pests use host plant odor to locate their host plant from a distance. Recent studies suggest that there are additional cues involved in insect landing on host plants. Researchers at the USDA-ARS laboratory in Hilo, HI, Cornell University in Geneva, NY, and Hobart and William Smith College in Geneva, NY evaluated the combinatory effect of water vapor and visual cues on the landing behavior of grape berry moth (GBM), a native specialist moth pest of juice and wine grapes in northeastern US. In flight tunnel, although GBM did not land on grape shoot odor based synthetic chemical attractant that they are attracted to, adding both water vapor and visual cue, a grape shoot mimic, to the synthetic attractant resulted in the same level of landing response equivalent to their response to real live grape shoot, suggesting that these additional cues can improve the effectiveness of traps used to manage female grape berry moth.

Technical Abstract: Many phytophagous insects locate their host plant using mixtures of volatile compounds produced by the plant. A key behavior in the host location process that has been the focus of decades of behavioral research is optomotor anemotaxis. Another key step in host location is landing on (or near) the odor source. In previous work, rubber septa emitting a synthetic blend of volatiles extracted from young shoots of grape plants, Vitus spp., elicited equivalent levels of oriented upwind flight by female grape berry moths (GBM; Paralobesia viteana) as did actual (control) grape shoots. However, in contrast to the shoots, females did not land on the odor source. In this study, we used flight tunnel assays to investigate the landing response of GBM females with respect to chemical and visual stimuli, as well as differences in relative humidity. When stimuli were presented individually, only the synthetic blend of host plant volatiles elicited equivalent levels of oriented upwind flight compared to the plants. Interestingly, wet cotton strips elicited low but consistent levels of upwind flight. In paired assays, only the synthetic blend paired with wet cotton strips elicited landing, although at significantly lower levels than that elicited by grape shoots. To achieve landing rates equivalent to live grape shoots, grape berry moth females required all three stimuli we tested: host odor cues, moisture, and visual cues simulating a grape shoot. These results suggest the cues have a synergistic effect, and that landing behavior requires complex sensory processing using multiple sensory inputs. Furthermore, these results suggest that moisture plays an important role in the host plant location process.